You must login as a root user, if not root user then switch to root user using following command:
$ su -
Create the directory i.e. mount point:
# mkdir -p /mnt/disk
Use mount command as follows to mount iso file called disk1.iso:
# mount -o loop disk1.iso /mnt/disk
Change directory to list files stored inside an ISO image:
# cd /mnt/disk # ls -l